This invention relates generally to highway trucks and trailers, particularly to a pair of trailers. The front trailer mounts on a fifth wheel on the rear of the truck and has a single rear axle and the rear trailer has a front and real axle and connects at its front end to the rear of the front trailer. The body of each trailer has a configuration which is capable of conversion from a flat-bed configuration to a gondola configuration.
In the lumber industry it has become common practice for lumber pieces, which become scraps at the lumber mill because they cannot be made into commercial cuts, to be turned into wood chips which are used as a source of energy for powering the mill. In hauling commercial lumber from the mill, to a use location, often several hundred miles away, it is economical for the trucks which haul the finished lumber to the job site to carry back a load of chips for generation of energy at the mill.
Finished lumber is typically banded together in units which constitute a particular customers order. These units are loaded by forklift onto a flat-bed trailer for hauling. When these lumber units are delivered to the job site area, the trailers must return to the mill empty even though a substantial supply of chips may be available. This occurs because a flat-bed type trailer cannot haul wood chips. A gondola style trailer is necessary for hauling chips. Accordingly, substantial economies are available if the same flat-bed type trailers which haul banded finished lumber units to the construction site can be converted to a gondola style trailer. Then when a trucker using a flat-bed trailer to haul lumber to the construction location unloads he can convert his trailers to a gondola type trailer to be filled with wood chips for his return trip to the mill. However, at the mill he now has gondola type trailers, but he can easily convert them back to flat-bed trailers in order to haul finished lumber again.
Numerous trailers have been disclosed in the prior art which are convertible to different body configurations for different uses but none of these will provide the conversion from a flat-bed to a bulk materials body such as required in the lumber hauling industry. A patent search has revealed the following United States patents which are representative of this prior art:
U.S. Pat. No. 4,007,567 PA0 U.S. Pat. No. 4,302,044 PA0 U.S. Pat. No. 3,709,552 PA0 U.S. Pat. No. 4,545,611 PA0 U.S. Pat. No. 4,682,811 PA0 U.S. Pat. No. 2,263,105 PA0 U.S. Pat. No. 3,097,012 PA0 U.S. Pat. No. 3,181,909 PA0 U.S. Pat. No. 4,613,182 PA0 U.S. Pat. No. 4,526,417 PA0 U.S. Pat. No. 4,489,975
The patents to Broadbent, (U.S. Pat. No. 3,709,552); Bain (U.S. Pat. No. 2,097,012); and Stone (U.S. Pat. No. 4,613,182); show the most similar van bodies to my convertible trailer however none discloses a trailer which readily converts from a flat bed configuration to a gondola or bulk type body needed by the lumber industry. The other prior art disclosures are considerably less similar and are used for conversions which are not truly applicable.
I am now advised however, that a new trailer unit is now being marketed by Western Trailers of Boise Id. which provides conversion from a flat-bed body to a bulk materials body by using flexible material on rolls on each side, and forming an enclosing body by unrolling the materials and streching it over the side area. This trailer has substantial limitations however, in that the flexible material does not provide the needed support of a solid side-wall and is vulnerable to tearing by the materials being hauled or by engagement with foreign objects such as other vehicles or buildings.
It is a major object of this invention to provide trailers for a highway truck which are readily convertible from a flat-bed type to a gondola or bulk-material type trailer.
It also an important object of this invention to provide a lumber products trailer of the type described in which the hauling costs can be minimized by hauling finished lumber on the first leg of a haul and wood chips on the return leg.
It is a further object of this invention to provide a trailer of the type described in which an elevated generally rectangular frame is constructed on the trailer bed and opposing side panels are hinge mounted to the upper portion of the frame and disposed to swing upwardly from a generally vertical position on the trailer bed forming a gondola type trailer to a generally horizontal position forming an over-lapping top above the trailer flat-bed.
It is still another object of this invention to provide trailers which can be readily converted from a flat-bed to a gondola configuration which has split side panels of solid sheet material that join together and are staked to the trailer bed by lock braces when the side panels are serving as the vertical side walls forming a gondola type trailer and pivot into said over-lapping position on top of the trailer structure by means of electrical wenches when the trailer is used as a flat-bed.
It is a further object of this invention to provide a convertible trailer of the type described in which the cost of converting the trailer is substantially reduced, and the conversion time is minimal and can be readily achieved by a driver.